Short TTI patterns

ABSTRACT

There is disclosed a method of operating a terminal (10) in a wireless communication network, the method comprising receiving and/or transmitting according to a transmission time interval, TTI, configuration, the TTI configuration indicating at least one short transmitting time interval having between one or two and seven symbols of duration in a subframe. There are also disclosed related methods and devices.

PRIORITY

This application is a continuation, under 35 U.S.C. § 120, of U.S.patent application Ser. No. 16/324,668 filed on Feb. 11, 2019, which isa U.S. National Stage Filing under 35 U.S.C. § 371 of InternationalPatent Application Serial No. PCT/SE2017/050820 filed Aug. 14, 2017 andentitled “SHORT TTI PATTERNS” which claims priority to U.S. ProvisionalPatent Application No. 62/374,269 filed Aug. 12, 2016 each of which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

This disclosure pertains to wireless communication technology, inparticular in the context of short transmission time intervals.

BACKGROUND

Packet data latency is one of the performance metrics that vendors,operators and also end-users (via speed test applications) regularlymeasure. Latency measurements are done in all phases of a radio accessnetwork system lifetime, when verifying a new software release or systemcomponent, when deploying a system and when the system is in commercialoperation.

Shorter latency than previous generations of 3GPP RATs was oneperformance metric that guided the design of Long Term Evolution (LTE).LTE is also now recognized by the end-users to be a system that providesfaster access to internet and lower data latencies than previousgenerations of mobile radio technologies.

Packet data latency is important not only for the perceivedresponsiveness of the system; it is also a parameter that indirectlyinfluences the throughput of the system. HTTP/TCP is the dominatingapplication and transport layer protocol suite used on the internettoday. According to HTTP Archive (http://httparchive.org/trends.php) thetypical size of HTTP based transactions over the internet are in therange of a few 10's of Kbyte up to 1 Mbyte. In this size range, the TCPslow start period is a significant part of the total transport period ofthe packet stream. During TCP slow start, the performance is latencylimited. Hence, improved latency can rather easily be shown to improvethe average throughput, for this type of TCP based data transactions.

Radio resource efficiency could be positively impacted by latencyreductions. Lower packet data latency could increase the number oftransmissions possible within a certain delay bound; hence higher BlockError Rate (BLER) targets could be used for the data transmissionsfreeing up radio resources, potentially improving the capacity of thesystem.

SUMMARY

It is an object of this disclosure to provide approaches allowingimproved latency.

One possible area to address when it comes to packet latency reductions,is the reduction of transport time of data and control signaling, byaddressing the length of a transmission time interval (TTI). In LTErelease 8, a TTI corresponds to one subframe (SF) of length 1millisecond. One such 1 ms TTI is constructed by using 14 OFDM orSC-FDMA symbols in the case of normal cyclic prefix and 12 OFDM orSC-FDMA symbols in the case of extended cyclic prefix.

Accordingly, there is proposed a method of operating a terminal in awireless communication network. The method comprising receiving and/ortransmitting according to a transmission time interval, TTI,configuration. The TTI configuration indicates at least one shorttransmitting time interval having between one or two and seven symbolsof duration in a subframe.

A terminal for a wireless communication network may be considered. Theterminal is adapted for receiving and/or transmitting according to atransmission time interval, TTI, configuration. The TTI configurationindicates at least one short transmitting time interval having betweenone or two and seven symbols of duration in a subframe. The terminal maycomprise, and/or be adapted for utilising, processing circuitry(respectively control circuitry), and/or radio circuitry, in particulara receiver and/or transmitter and/or transceiver, for the receivingand/or transmitting, and/or for receiving the TTI configuration.Alternatively, or additionally, it may comprise a correspondingreceiving module and/or transmitting module.

The TTI configuration may configured by a network node.

In addition, a method of operating a network node in a wirelesscommunication network is considered. The network node is adapted forconfiguring a terminal with a transmission time interval, TTI,configuration for downlink communication and/or uplink transmission. TheTTI configuration indicates at least one short transmitting timeinterval having between one or two and seven symbols of duration in asubframe.

Also, a network node for a wireless communication network is described.The network node is adapted for configuring a terminal with atransmission time interval, TTI, configuration for downlinkcommunication and/or uplink transmission. The TTI configurationindicates at least one short transmitting time interval having betweenone or two and seven symbols of duration in a subframe. The network nodemay comprise, and/or be adapted for utilising, processing circuitry(respectively control circuitry), and/or radio circuitry, in particulara transmitter and/or transceiver, for the configuring. Alternatively, oradditionally, it may comprise a corresponding configuring module.

The short transmission time interval in general may be limited to,and/or arranged in, and/or comprised in, and/or confined to, one slot ofthe subframe, e.g. the first or second slot, and/or may be arranged tonot cross from one slot to the next.

There is also considered a program product comprising code executable byprocessing circuitry and/or control circuitry, the code causing theprocessing circuitry and/or control circuitry to carry out and/orcontrol a method as described herein.

A carrier medium carrying and/or storing a program product as describedherein is also described.

The approaches described herein allow low-latency application already atthe TTI level, facilitating easy configuration with little additionaloverhead. The TTI configuration may in particular additionally indicateor schedule or configure reference signaling, e.g. CRS and/or CSI-RSsignaling, e.g. in the subframe. A TTI configuration may be configuredfor a subframe with controls signaling, e.g. DCI and/or PDCCH signalingin the same subframe, e.g. in a control region at the beginning of thesubframe.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are provided to illustrate concepts and approachesdescribed herein, and are not intended to limit their scope. Thedrawings comprise:

FIG. 1 , showing an exemplary TTI configuration;

FIG. 2 , showing additional exemplary TTI configurations;

FIG. 3 , showing additional exemplary TTI configurations;

FIG. 4 , showing additional exemplary TTI configurations;

FIG. 5 , showing an exemplary network node;

FIG. 6 , showing an exemplary terminal;

FIG. 7 , showing additional exemplary TTI configurations;

FIG. 8 , showing additional exemplary TTI configurations; and

FIG. 9 , showing additional exemplary TTI configurations.

DETAILED DESCRIPTION

Short(er) TTIs can be decided to have any duration in time and compriseresources on a number of OFDM or SC-FDMA symbols within a 1 ms SF. Asone example, the duration of the short TTI may be 0.5 ms, i.e. sevenOFDM or SC-FDMA symbols for the case with normal cyclic prefix. Asanother example, the duration of the short TTI may be 2 symbols. It maybe considered that a sTTI has a duration between one, preferably 2, and7 symbols. A TTI pattern may be adapted accordingly to cover the sTTIduration. A LTE subframe comprises two slots, each of 0.5 ms duration.Usually, symbols 0 to 6 are associated to the first slot (slot 0), andsymbols 7 to 13 to the second slot (slot 1).

CSI-RS is an example of reference signaling. The Channel StateInformation Reference Signal (CSI-RS) is a cell specific signal spanningtwo consecutive symbols in downlink, as shown in FIG. 1 . There are 20different CSI-RS positions possible in a subframe. A cell may forexample be configured with one, two, four, or eight CSI-RS according topredefined patterns. In the case of one CSI-RS, the pattern for twoCSI-RS may be used. The slot border between slot 0 and slot 1 is markedwith a broadened line between symbols 6 and 7.

CSI-RS is used by the network (e.g. in cooperation with a terminalperforming a CSI procedure) to acquire channel state information and toestimate the interference. CSI-RS can be of zero power (muted), whichmakes it possible for a UE to measure on another cell than its servingcell, and also to measure on configured CSI-IM (InterferenceMeasurement) resources, defined as a zero-power CSI-RS resource intendedfor interference measurement.

DL (Downlink) patterns for short TTI operations may not be not confinedto the slot, such that legacy LTE CSI-RS pattern may end up in multipleshort TTI. If a CSI-IM measurement is performed in a neighboring celland the two symbols correspond to two different short TTI transmissionswith different characteristics, the measurement quality may be impacted.

There are presented DL short TTI patterns that contain whole CSI-RS,which may be aligned at a symbol index or border, allowing a broad rangeof, or a change of TTI lengths. The TTI patterns may be defined suchthat they do not cross a slot border within a subframe, and/or may be inone version, limited to the first slot of a subframe (slot 0). Thepatterns for TTI may be multiplexed in time and/or over severalchannels, as described herein. Alternatively, or additionally, one ormore patterns may be time-aligned at a specific symbol or a symbolborder, which may be represented by the associated symbol index. Forexample, the symbol aligned to may be the first symbol of the next slot,respectively the leading (in time) border of this symbol, which may beconsidered to correspond to the trailing (in time) border of the lastsymbol of the current slot.

The proposed solution supports in particular downlink short TTItransmissions while maintaining the quality of CSI-RS measurements whichare an important part of channel and interference estimation.

By confining the short TTIs within a slot, the short TTI length can bechanged (switching between patterns) at the slot border and/or betweensubframes. There also exists a frequency-hopping resource allocationscheme (resource allocation of type 2 with virtual resource blocks)where frequency allocation can change between the slots.

New patterns for short TTI transmission in DL may be defined based onone or more of the following conditions:

-   -   The short TTIs are defined as part of the PDSCH in the DL        subframe; and/or    -   The short TTIs are aligned at a symbol with a given index (e.g.        7), in particular a border thereof, for example the border        leading in time (e.g. they do not cross the slot        border=alignment at symbol index 7); and/or    -   The CSI-RS/IM pairs are contained in one short TTI; and/or    -   The short TTIs should be of the designated length (e.g. 2 or 7        symbols) when possible.

The above conditions taken together may lead to patterns exemplarilyshown in FIG. 2 .

Generally, a TTI pattern (sTTI pattern) may be represented by and/orassociated to a TTI duration or length, and/or may be defined orarranged in a subframe structure.

As seen in the figure, for the 2 symbol TTI case, some TTIs are forcedor extended to a length of 3 symbols. This can be done in several ways,and two options are shown in the figure.

FIG. 3 shows two cases where the split is changed for 1os (OFDM symbollength) PDCCH. This is done to keep the number of TTIs the same (alwaysfive), independent on number of used PDCCH symbols.

As an embodiment, the position of the longer TTIs in the 2 symbol caseare chosen so that they contain multiple UL DCI (Downlink ControlInformation) as required by the UL short TTI scheduling. This may happenin the case of 6 or 8 UL short TTI per subframe and only 5 DL short TTIper subframe, thus requiring more than one UL short TTI to be scheduledfrom one DL short TTI. The flexibility in the DL pattern can then beused to place the longer TTIs where the extra UL DCI messages arerequired. This may depends on the UL timing.

Another way to allow for time-multiplexing of sTTIs with differentlengths is to have a sTTI ending at the same OFDM symbol for alldifferent configurations. This symbol does not necessarily need to bethe last symbol of the first slot of a subframe. This would not allowthe frequency-hopping allocation, but may have the advantage of moreequal TTI lengths. An example of this is shown in FIG. 4 with 3 symboland 6 symbol TTI length.

Generally, to each subframe or slot, there may be associated one or moreTTI patterns and/or TTI lengths, such that one or more TTI patterns maybe included in one slot or a subframe. A TTI pattern may pertain todownlink and/or uplink transmissions. In a subframe, there may bearranged or allocated TTI patterns comprising or scheduling downlinktransmissions, uplink transmission, or both. To a TTI pattern, there maybe associated, or be assigned (e.g., such that the TTI patternscomprises), a reference signaling pattern (RS pattern), and/or a controlchannel pattern. A RS pattern may for example comprise a CSI-RS patternand/or CRS pattern, for example in or for DL, and/or a SRS pattern, e.g.in or for uplink. A control channel pattern may pertain to one or morephysical control channels, e.g. for example PDCCH and/or PUCCH.

A pattern, like TTI pattern, or a reference signaling pattern (of a TTIpattern) may define the resource distribution, in particular intime/frequency and/or power, used for TTI pattern, or the referencesignaling respectively its transmission. A pattern may be defined inregard to, and/or comprise or indicate, a density (of symbols orsignaling) in time and/or frequency, e.g. in terms of how may REs and/orsymbols are transmitted in a given time interval like a TTI or subframeor slot, and/or on a carrier or frequency range, in particularpertaining to the number of subcarrier used for RS transmission.Generally, to different beamforming states and/or different beamreception states, there may be associated different patterns.

FIG. 5 schematically show a network node or base station 100, which inparticular may be an eNodeB. Network node 100 comprises controlcircuitry 120, which may comprise a controller connected to a memory.Any module, e.g. receiving module and/or transmitting module and/orcontrol or processing module, of the network node may be implemented inand/or executable by the control circuitry 120. The control circuitry isconnected to control radio circuitry 122 of the network node 100, whichprovides receiver and transmitter and/or transceiver functionality. Anantenna circuitry 124 may be connected or connectable to radio circuitry122 for signal reception or transmittance and/or amplification. Thenetwork node 100 may be adapted to carry out any of the methods foroperating a network node disclosed herein; in particular, it maycomprise corresponding circuitry, e.g. control circuitry. The antennacircuitry may be connected to and/or comprise an antenna array.

FIG. 6 schematically shows a terminal 10, which may be implemented inthis example as a user equipment. Terminal 10 comprises controlcircuitry 20, which may comprise a controller connected to a memory. Anymodule of the terminal, e.g. receiving module and/or transmitting moduleand/or control or processing module, may be implemented in and/orexecutable by, the control circuitry 20, in particular as module in thecontroller. Terminal 10 also comprises radio circuitry 22 providingreceiving and transmitting or transceiving functionality, the radiocircuitry 22 connected or connectable to the control circuitry. Anantenna circuitry 24 of the terminal 10 is connected or connectable tothe radio circuitry 22 to collect or send and/or amplify signals. Radiocircuitry 22 and the control circuitry 20 controlling it are configuredfor cellular communication with a network on a first cell/carrier and asecond cell/carrier, in particular utilizing E-UTRAN/LTE resources asdescribed herein. The terminal 10 may be adapted to carry out any of themethods for operating a terminal disclosed herein; in particular, it maycomprise corresponding circuitry, e.g. control circuitry.

Alternatively, or additionally, there may be considered generally thefollowing:

It is discussed how different TTIs can be supported in LTE and what theimplications on HARQ and grant timing are.

1.1 DL Subframes

Short TTI in a subframe for two different (sTTI) lengths is described:2os (OFDMA-symbol time length) and 7os. To simplify the definition of ULgrant timing and DL HARQ timing, it is proposed that the DL TTIs havefixed starting positions and that the length of the first DL TTI, and insome cases the number of DL TTIs, varies depending on the number ofsymbols used for PDCCH, see FIG. 7 . Since the longest PDCCH length of 4OFDM symbols is intended for narrowband operation, it is proposed not tobe used for short TTI operation, since the control overhead may becometoo large.

When defining the positions of a 2-symbol DL sTTI within the subframe,the CSI-RS pattern should be considered so that a CSI-RS pair in timedomain does not overlap two consecutive DL TTIs but is contained in asingle sTTI. This enables to combine the sTTI feature with CSI-RS basedtransmission modes, especially to obtain accurate interferencemeasurement with CSI-IM.

FIG. 7 shows TTIs in DL subframe for different TTI lengths and PDCCHlengths. R and C denote a OFDM symbol with CRS and potential CSI-RS,respectively.

Proposal 1 Aim at that a DL TTI length corresponds to fixed startingsymbols of TTIs in PDSCH

Proposal 2 PDCCH length of 4 should not be supported for short TTIoperation.

Proposal 3 sTTI position is designed so that it does not partly overlapwith potential CSI-RS resources

The timing for transmitting DL HARQ in UL needs to be well defined, itmay be indicated to the UE separately from the DL assignment. To keepthe payload of each sPUCCH low, the DL HARQ should be distributed overthe UL subframe, which may depend on the length of sPUCCH. Also,multiplexing capabilities should be considered. A fixed mapping from DLTTI to sPUCCH for a certain DL TTI and sPUCCH combination is proposed.

Proposal 4 The DL HARQ timing is fixed for a combination of DL and ULTTI for sPUCCH.

1.2 UL Subframes

1.2.1 sPUCCH

For sPUCCH a certain TTI length may correspond to different TTIconfigurations depending on if the DMRS are shared or not. In FIG. 8 ,examples for TTI lengths of 2, 4, and 7os with and without SRS in thelast symbol are given. For a given configuration the TTIs have fixedstarting positions, and are placed such that the TTIs do not cross theslot-border. This way, slot-based frequency hopping is possible.

FIG. 8 shows TTIs for sPUSCH in UL subframe for one realization of thedifferent options of TTI lengths, where R denotes reference symbol and SSRS position (if scheduled).

Observation 1 . . . Different UL TTI configurations can be defined foran UL TTI length.

Proposal 5. Aim at that an UL TTI configuration corresponds to fixedstarting symbols of TTIs in PUSCH.

Proposal 6 . . . Uplink sTTI transmission is not mapped acrossslot-boundary.

Proposal 7 . . . It is recommended to support 2/3 symbols sPUSCH forlowest latency, and 4 and 7 symbols sPUSCH for reduced latency withhigher TBS.

The UL grant for the UL sTTI should be transmitted in the sPDCCH insidethe DL sTTI. The number of TTIs in DL can be fewer in someconfigurations. For example, only 5 DL TTIs are included within onesub-frame, see FIG. 7 , for an sPDCCH of 3 symbols and DL TTIs of 2symbols. According to FIG. 2 , up to 8 TTIs in an UL sub-frame may beprovided. A possibility to send at least 2 UL grants within one DL sTTImay be considered. Each UL grant should then specify which of twopossible UL TTIs that is granted, if not implicit from location.

Proposal 8 The time from UL grant to sPUSCH transmission is based on acombination of sPDCCH timing and configuration in UL grant.

1.2.2 sPUCCH

The pattern of sPUCCH TTI may differ from that of sPUSCH. For theshortest DL TTI of 2 symbols, the sPUCCH should be equally long as theDL TTI to provide the shortest delay and to avoid multiplexing orbundling HARQ. This also allows for a simple 1-1 mapping between a DLTTI and the sPUCCH in which HARQ feedback is transmitted. More than 6sPUCCH per subframe is not required since this corresponds to themaximum number of DL sTTI in a subframe. The sPUCCH should, if possible,be aligned to the sPUSCH of FIG. 2 . This is to avoid overlappingtransmissions from a UE. Different patterns may be used if the subframecontains SRS.

FIG. 9 shows TTIs for sPUCCH of different length. For 4os and 7os TTIfrequency hopping between F1 and F2 is possible. S denotes symbol withSRS, and orange denotes symbol shared between users.

Two sPUCCH concepts may refer to a short and a long sPUCCH. In additionto the shorter sPUCCH solution described above, a longer sPUCCH may beprovided for improved coverage. For TDD operation, and for CA support,also higher payloads may be provided. A 7 symbol sPUCCH based on PF3 orPF4 would fulfill the requirements on improved coverage and increasedpayload, and also provide sufficiently low latency.

Also a 4 symbol sPUCCH should be specified if a 4 symbol sPUSCH isspecified, since it is much easier if the TTI of PUSCH and PUCCH is thesame, as discussed below.

Proposal 9. Define sPUCCH of 2/3 symbols TTI, to support SR andHARQ-ACK, and sPUCCH of 4 and 7 symbols for improved coverage andincreased payload.

1.3 TTI Length Combinations

It should be possible to combine the TTI lengths in DL and UL asdescribed above. For overhead and payload reasons it may make sense touse a longer TTI for UL data if latency needs are less strict, and forcoverage reasons a longer sPUCCH may be important. However, it isreasonable to limit the combinations so that scheduling and feedback donot become overly complex.

Proposal 10 . . . Specify the allowed combinations of a DL TTI lengthand the allowed UL TTI length

If the UL TTI is shorter than the DL TTI, multiple UL grants may beneeded in one DL TTI. For coverage reasons the sPUCCH TTI should only beas short as the DL TTI, or longer. Thus, it is proposed that the UL TTIlengths (sPUSCH and sPUCCH) are the same or longer than the DL TTI.

Proposal 11 . . . UL TTI length for sPUSCH and sPUCCH can be equal orlonger than DL TTI length.

The sPUCCH TTI length could in principle be set independently of thePUSCH TTI length, since the period of sPUCCH is more connected to DLTTI, as payload and timing should be properly set. However, tofacilitate the UCI mapping on sPUSCH and ensure sufficient UCIperformance on sPUSCH, the TTI length of sPUSCH should be the same orlonger than the one of sPUCCH. In general, if a 7-symbol sPUCCH wasconfigured by eNB for a given UE due to coverage issue or high sPUCCHpayload, it is very likely that a 7-symbol sPUSCH is also preferable forthe same reasons. Also the start of the sPUCCH and sPUSCH should bealigned, or a rule is needed to move UCI to sPUSCH when they overlap.

Proposal 12 . . . TTI length for sPUSCH and sPUCCH are equal, and thestart of TTIs are aligned.

With the TTI lengths discussed above the most relevant TTI combinationsto consider are those listed in Table 1. Case 1 also increasesscheduling complexity but may be required for improved sPUCCH coverage.

Proposal 13 Four combinations of TTI lengths should be available forshort TTI operation:

sPUSCH/sPUSCH/sPUCCH lengths 2/2/2, 2/4/4, 2/7/7, and 7/7/7 symbols.

TABLE 1 Relevant short TTI combinations to consider. sPDSCH/sPDCCHsPUSCH sPUCCH Case TTI TTI TTI Use case 0 2os 2os 2os Lowest latency 12os 4os 4os Lowest DL latency, low UL latency 2 2os 7os 7os Lowest DLlatency with improved UL coverage and reduced UL latency 3 7os 7os 7osReduced latency

1.3.1 Switching Between sTTI Cases

It should be possible to change sTTI case (as described above) betweensubframes, and also to move individual users from one case to another.As an example, it may be considered all users starting in sTTI case 0.This can be indicated over RRC, or in PDCCH as lowest latency normaloperation. A user who loses UL coverage is then identified by thenetwork and is moved to case 1 or 2 (indicated e.g. with fast DCI orRRC). By the use of split allocations, it is possible to serve userswith different TTI lengths in the same sTTI band. It should be notedthat when moving users from one case to another, the delay before thechanged UL sTTI length is valid needs to be defined.

Proposal 14 It should be possible to individually move users betweensTTI cases.

Proposal 15 It should be possible to run different cases simultaneouslyin UL and DL.

The following observation is discussed:

Observation 1 . . . Different UL TTI configurations can be defined foran UL TTI length.

Based on the discussion, the following proposals may be considered:

Proposal 1 . . . Aim at that a DL TTI length corresponds to fixedstarting symbols of TTIs in PDSCH

Proposal 2 . . . PDCCH length of 4 should not be supported for short TTIoperation.

Proposal 3 sTTI position is designed so that it does not partly overlapwith potential CSI-RS resources

Proposal 4 The DL HARQ timing is fixed for a combination of DL and ULTTI for sPUCCH.

Proposal 5 Aim at that an UL TTI configuration corresponds to fixedstarting symbols of TTIs in PUSCH.

Proposal 6 . . . Uplink sTTI transmission is not mapped acrossslot-boundary.

Proposal 7 . . . It is recommended to support 2/3 symbols sPUSCH forlowest latency, and 4 and 7 symbols sPUSCH for reduced latency withhigher TBS.

Proposal 8 The time from UL grant to sPUSCH transmission is based on acombination of sPDCCH timing and configuration in UL grant.

Proposal 9 . . . Define sPUCCH of 2/3 symbols TTI, to support SR andHARQ-ACK, and sPUCCH of 4 and 7 symbols for improved coverage andincreased payload.

Proposal 10 Specify the allowed combinations of a DL TTI length insub-frame “N” and the allowed TTI length in the UL subframe “N+D” inwhich DL HARQ is transmitted (corresponding to sub-frame “N”) and inwhich the UL grants are valid (transmitted in sub-frame “N”).

Proposal 11 . . . UL TTI length for sPUSCH and sPUCCH can be equal orlonger than DL TTI length.

Proposal 12 TTI length for sPUSCH and sPUCCH are equal, and the start ofTTIs are aligned.

Proposal 13 . . . Four combinations of TTI lengths should be availablefor short TTI operation: sPDSCH/sPUSCH/sPUCCH lengths 2/2/2, 2/4/4,2/7/7, and 7/7/7 symbols.

Proposal 14 It should be possible to individually move users betweensTTI cases.

Proposal 15 It should be possible to run different cases simultaneouslyin UL and DL.

These proposals may be considered to be independent from each other,such that they may be implemented individually, or in any suitablecombination.

There may be considered a (first) network node adapted for DLtransmitting according to one of the proposals for DL transmissiondescribed herein, in particular according to one of the DL patterns, inparticular DL sTTI patterns, and/or TTI lengths described herein, and/oraccording to one or any combination of the conditions discussed herein.

Transmitting may be based on, and/or the network node may be adaptedfor, determining a pattern to be used. The network node may be adaptedfor, and/or comprise a switching module for, switching between differentpatterns. Such switching may occur e.g. between subframes. The networknode may generally comprise a transmitting module for DL transmitting,and/or a determining module for determining a pattern. Determining thepattern may be based on operation conditions, in particular on latencyrequirements. Transmitting may generally pertain to wireless or radiotransmissions.

Alternatively, there may be considered a (second) network node adaptedfor configuring a terminal like a UE with a TTI configuration for DLcommunication (reception) and/or UL transmission according to one ormore DL TTI patterns and/or UL TTI patterns and/or any one, or anycombination of, the conditions described herein. The network node maycomprise a corresponding configuring module. The network node may alsobe adapted as a (first) network node described above.

Any of the network node/s may be a network node for a wirelesscommunication network.

Moreover, there may be considered a (first) method of operating anetwork node in a wireless communication network, e.g. of operating a(first) network node as described herein. The method may comprise DLtransmitting according to one of the proposals 495 for DL transmissiondescribed herein, in particular according to one of the DL patterns, inparticular DL sTTI patterns, and/or TTI lengths described herein, and/oraccording to one or any combination of the conditions discussed herein.Transmitting may be based on, and/or the method may comprise,determining a pattern to be used. The method optionally may compriseswitching between different patterns. Such switching may occur e.g.between subframes. Determining the pattern may be based on operationconditions, in particular on latency requirements.

Alternatively, there may be considered a (second) method of operating anetwork node in a wireless communication network, which may be a(second) network node described herein. This method may compriseconfiguring a terminal like a UE with a TTI configuration for DLcommunication (reception) and/or UL transmission according to one ormore DL TTI patterns and/or UL TTI patterns and/or any one or anycombination of conditions described herein. The method may also compriseactions and/or the actions of the (first) method for operating a networknode described above.

Generally, there may be considered a terminal for a wirelesscommunication network. The terminal may be implemented as a UE. Theterminal may be adapted for receiving and/or transmitting according to aTTI configuration.

Also, there is disclosed a method of operating a terminal in a wirelesscommunication network. The terminal may be implemented as a UE. Themethod comprises receiving and/or transmitting according to a TTIconfiguration. The method may comprise receiving the TTI configuration,e.g. from a network node, which may be a (second) network node asdescribed herein.

A TTI configuration may generally pertain to DL communication(reception) and/or UL transmission according to one or more DL TTIpatterns and/or one or more UL TTI patterns and/or any one, or anycombination of, the conditions described herein. The terminal maycomprise a receiving module for receiving the configuration, e.g. from anetwork node, which may be a (second) network node as described herein.A TTI configuration may define and/or pertain to a slot and/or asubframe. A configuration may generally be valid over a plurality ofslots and/or subframes.

There may be considered a wireless transmitter and/or network nodeadapted for performing any one of the methods for operating a wirelesstransmitter and/or network node described herein.

There may be considered a terminal adapted for performing any one of themethods for operating a terminal described herein.

There is also disclosed a program product comprising code executable bycontrol circuitry, the code causing the control circuitry to carry outand/or control any one of the method for operating a terminal or networknode as described herein, in particular if executed on controlcircuitry, which may be control circuitry of a terminal or a networknode as described herein.

Moreover, there is disclosed a carrier medium carrying and/or storing atleast any one of the program products described herein and/or codeexecutable by control circuitry, the code causing the control circuitryto perform and/or control at least any one of the methods describedherein. Generally, a carrier medium may be accessible and/or readableand/or receivable by control circuitry. Storing data and/or a programproduct and/or code may be seen as part of carrying data and/or aprogram product and/or code. A carrier medium generally may comprise aguiding/transporting medium and/or a storage medium. Aguiding/transporting medium may be adapted to carry and/or carry and/orstore signals, in particular electromagnetic signals and/or electricalsignals and/or magnetic signals and/or optical signals. A carriermedium, in particular a guiding/transporting medium, may be adapted toguide such signals to carry them. A carrier medium, in particular aguiding/transporting medium, may comprise the electromagnetic field,e.g. radio waves or microwaves, and/or optically transmissive material,e.g. glass fiber, and/or cable. A storage medium may comprise at leastone of a memory, which may be volatile or non-volatile, a buffer, acache, an optical disc, magnetic memory, flash memory, etc.

Reference signaling may comprise one or more reference signals orsymbols. Reference signals may be adapted or intended for a receiver(e.g., a terminal) to perform measurements on and/or to provide ameasurement report on. Reference signals may be defined by a standard,e.g. CSI-RS defined by LTE. Measurement reporting and/or providing ameasurement report may generally comprise transmitting a measurementreport, in particular to a source/transmitter of reference signaling,e.g. a transmitting node or network node, and/or performingmeasurements, e.g. on reference signaling, and/or evaluatingmeasurements (e.g., processing the measurement results).

A measurement report may be based on the performed measurements and/orthe evaluating. Generally, reference signaling may be cell-specific orreceiver-specific. CSI-RS may be considered an example forreceiver-specific reference signaling. Receiver-specific referencesignaling may be intended for a specific receiver to performmeasurements on, the receiver may be configured accordingly.Cell-specific reference signaling may be intended for all (or at leastan unspecified number of) receivers in the cell to perform measurementson. Transmitting a reference signaling on more than one antenna elementmay comprise beamforming (e.g., of the reference signaling).Transmitting different reference signalings (e.g., a first and a secondreference signaling), and/or on different antenna elements (for the sameand/or different reference signaling) may be performed simultaneously,e.g. in the same time interval (e.g., symbol time interval, which mayassociated to a subframe), and/or such that symbols or signals of onereference signaling coincide with symbols or signals of the otherreference signaling. A symbol of a reference signal may cover and/orcomprise and/or represent one Resource Element, and/or a symbol timeinterval and an associated frequency range, e.g. a subcarrier. Referencesignaling may be represented by a pattern, e.g. in time/frequency space.The pattern may represent symbols and/or signals and/or resources (e.g.,REs), respectively their distribution (in particular, in time/frequencyand/or power) used for the reference signaling, in particular in a giventime interval, e.g. a TTI and/or over a subframe of slot. Examples forreference signaling comprise in particular CSI-RS, but also CRS and SRS.

Configuring (e.g., with or for a configuration) a device like a terminalor network node may comprise bringing the device into a state inaccordance with the configuration. A device may generally configureitself, e.g. by adapting a configuration. Configuring a terminal, e.g.by a network node, may comprise transmitting a configuration orconfiguration data indicating a configuration to the terminal, and/orinstructing the terminal, e.g. via transmission of configuration data,to adapt the configuration configured.

A configuration may in particular pertain to measurement reporting, e.g.to a CSI process. Measurement reporting may generally pertain tospecific signaling (or an associated port), which may be indicated orconfigured to the terminal by the network or network node, e.g. bytransmitting corresponding configuration data. Measurement reporting maygenerally indicate a preferred port or port combination (or precoder orprecoder combination) to be used, which may be referred to as port orprecoder selection. In particular, a configuration may indicate thepattern determined for RS and/or used for RS transmission (e.g., by thenetwork node), in particular CSI-RS.

A scheduling grant (e.g., uplink grant) may represent control signaling(e.g., downlink control information/signaling). It may be consideredthat a scheduling grant configures the signaling resource range and/orresources for uplink signaling, in particular uplink control signalingand/or feedback signaling, e.g. acknowledgement signaling. Configuringthe signaling resource range and/or resources may comprise configuringor scheduling it for transmission by the configured radio node. Ascheduling grant may indicate a channel and/or possible channels to beused/usable for the feedback signaling, in particular whether a sharedchannel like a PUSCH may be used/is to be used. A scheduling grant maygenerally indicate uplink resource/s and/or an uplink channel and/or aformat for control information pertaining to associated schedulingassignments. Both grant and assignment/s may be considered (downlink orsidelink) control information, and/or be associated to, and/ortransmitted with, different messages. A scheduling grant or UL grant maybe implemented as DCI transmission, e.g. on PDCCH (Physical DownlinkControl Channel).

A scheduling assignment (e.g., DL assignment) may be configured withcontrol signaling, e.g. downlink control signaling like DCI signaling.Such control signaling may be considered to represent and/or comprisescheduling signaling, which may indicate scheduling information. Ascheduling assignment may be considered scheduling informationindicating scheduling of signaling/transmission of signaling, inparticular pertaining to signaling received or to be received by thedevice configured with the scheduling assignment. It may be consideredthat a scheduling assignment may indicate data (e.g., data block orelement and/or channel and/or data stream) and/or an (associated)acknowledgement signaling process and/or resource/s on which the data(or, in some cases, reference signaling) is to be received and/orindicate resource/s for associated feedback signaling, and/or a feedbackresource range on which associated feedback signaling is to betransmitted. Transmission associated to an acknowledgement signalingprocess, and/or the associated resources or resource structure, may beconfigured and/or scheduled, for example by a scheduling assignment.Different scheduling assignments may be associated to differentacknowledgement signaling processes. A scheduling assignment may beconsidered an example of downlink control information or signaling, e.g.if transmitted by a network node and/or provided on downlink. Ascheduling assignment may be signaled on a PDCCH.

Transmitting in downlink may pertain to transmission from the network ornetwork node to the terminal. Transmitting in uplink may pertain totransmission from the terminal to the network or network node. Uplinkand downlink may be considered communication directions.

A measurement process like a CSI process may generally comprisereceiving (e.g., by a UE), from a transmitting node or network node,reference signaling (CSI-RS), and providing a report like measurementreport based on the received reference signaling. The report ormeasurement report may in particular indicate or comprise CSIinformation, in particular CQI (Channel Quality Indicator), PMI(Precoding Matrix Indicator) and/or RI (Rank Indicator), and/or a beamselection report or indication indicating which beam is selected by themeasuring device like a terminal.

In the context of this description, wireless communication may becommunication, in particular transmission and/or reception of data, viaelectromagnetic waves and/or an air interface, in particular radiowaves, e.g. in a wireless communication network and/or utilizing a radioaccess technology (RAT). The communication may involve one or more thanone terminal connected to a wireless communication network and/or morethan one node of a wireless communication network and/or in a wirelesscommunication network. It may be envisioned that a node in or forcommunication, and/or in, of or for a wireless communication network isadapted for communication utilizing one or more RATs, in particularLTE/E-UTRA. A communication may generally involve transmitting and/orreceiving messages, in particular in the form of packet data. A messageor packet may comprise control and/or configuration data and/or payloaddata and/or represent and/or comprise a batch of physical layertransmissions. Control and/or configuration data may refer to datapertaining to the process of communication and/or nodes and/or terminalsof the communication. It may, e.g., include address data referring to anode or terminal of the communication and/or data pertaining to thetransmission mode and/or spectral configuration and/or frequency and/orcoding and/or timing and/or bandwidth as data pertaining to the processof communication or transmission, e.g. in a header.

Each node or terminal involved in communication may comprise radiocircuitry and/or control circuitry and/or antenna circuitry, which maybe arranged to utilize and/or implement one or more than one radioaccess technologies. Radio circuitry of a node or terminal may generallybe adapted for the transmission and/or reception of radio waves, and inparticular may comprise a corresponding transmitter and/or receiverand/or transceiver, which may be connected or connectable to antennacircuitry and/or control circuitry. Control circuitry of a node orterminal may comprise a controller and/or memory arranged to beaccessible for the controller for read and/or write access. Thecontroller may be arranged to control the communication and/or the radiocircuitry and/or provide additional services. Circuitry of a node orterminal, in particular control circuitry, e.g. a controller, may beprogrammed to provide the functionality described herein. Acorresponding program code may be stored in an associated memory and/orstorage medium and/or be hardwired and/or provided as firmware and/orsoftware and/or in hardware. A controller may generally comprise aprocessor and/or microprocessor and/or microcontroller and/or FPGA(Field-Programmable Gate Array) device and/or ASIC (Application SpecificIntegrated Circuit) device. More specifically, it may be considered thatcontrol circuitry comprises and/or may be connected or connectable tomemory, which may be adapted to be accessible for reading and/or writingby the controller and/or control circuitry. Radio access technology maygenerally comprise, e.g., Bluetooth and/or Wifi and/or WIMAX and/orcdma2000 and/or GERAN and/or UTRAN and/or in particular E-Utran and/orLTE. A communication may in particular comprise a physical layer (PHY)transmission and/or reception, onto which logical channels and/orlogical transmission and/or receptions may be imprinted or layered.

A wireless or cellular network may comprise a network node, inparticular a radio network node, which may be connected or connectableto a core network, e.g. a core network with an evolved network core,e.g. according to LTE. A network node may e.g. be a base station. Theconnection between the network node and the core network/network coremay be at least partly based on a cable/landline connection. Operationand/or communication and/or exchange of signals involving part of thecore network, in particular layers above a base station or eNB, and/orvia a predefined cell structure provided by a base station or eNB, maybe considered to be of cellular nature or be called cellular operation.Operation and/or communication and/or exchange of signals withoutinvolvement of layers above a base station and/or without utilizing apredefined cell structure provided by a base station or eNB, may beconsidered to be D2D communication or operation, in particular, if itutilises the radio resources, in particular carriers and/or frequencies,and/or equipment (e.g. circuitry like radio circuitry and/or antennacircuitry, in particular transmitter and/or receiver and/or transceiver)provided and/or used for cellular operation.

A terminal may be implemented as a user equipment. A terminal or a userequipment (UE) may generally be a device configured for wirelessdevice-to-device communication and/or a terminal for a wireless and/orcellular network, in particular a mobile terminal, for example a mobilephone, smart phone, tablet, PDA, etc. A user equipment or terminal maybe a node of or for a wireless communication network as describedherein, e.g. if it takes over some control and/or relay functionalityfor another terminal or node. It may be envisioned that terminal or auser equipment is adapted for one or more RATs, in particularLTE/E-UTRA. A terminal or user equipment may generally be proximityservices (ProSe) enabled, which may mean it is D2D capable or enabled.It may be considered that a terminal or user equipment comprises radiocircuitry and/control circuitry for wireless communication. Radiocircuitry may comprise for example a receiver device and/or transmitterdevice and/or transceiver device. Control circuitry may include acontroller, which may comprise a microprocessor and/or microcontrollerand/or FPGA (Field-Programmable Gate Array) device and/or ASIC(Application Specific Integrated Circuit) device. It may be consideredthat control circuitry comprises or may be connected or connectable tomemory, which may be adapted to be accessible for reading and/or writingby the controller and/or control circuitry. It may be considered that aterminal or user equipment is configured to be a terminal or userequipment adapted for LTE/E-UTRAN. Reference signaling in the uplink maybe associated to a terminal, e.g. SRS.

A network node or base station may be any kind of base station of awireless and/or cellular network adapted to serve one or more terminalsor user equipments. It may be considered that a base station is a nodeor network node of a wireless communication network. A network node orbase station may be adapted to provide and/or define and/or to serve oneor more cells of the network and/or to allocate frequency and/or timeresources for communication to one or more nodes or terminals of anetwork. Generally, any node adapted to provide such functionality maybe considered a base station. It may be considered that a base stationor more generally a network node, in particular a radio network node,comprises radio circuitry and/or control circuitry for wirelesscommunication. It may be envisioned that a base station or network nodeis adapted for one or more RATs, in particular LTE/E-UTRA. Radiocircuitry may comprise for example a receiver device and/or transmitterdevice and/or transceiver device, e.g., receiver and/or transmitterand/or transceiver. Control circuitry (which may also be referred to asprocessing circuitry) may include a controller, which may comprise amicroprocessor and/or microcontroller and/or FPGA (Field-ProgrammableGate Array) device and/or ASIC (Application Specific Integrated Circuit)device. It may be considered that control circuitry comprises or may beconnected or connectable to memory, which may be adapted to beaccessible for reading and/or writing by the controller and/or controlcircuitry. A base station may be arranged to be a node of a wirelesscommunication network, in particular configured for and/or to enableand/or to facilitate and/or to participate in cellular communication,e.g. as a device directly involved or as an auxiliary and/orcoordinating node. Generally, a base station may be arranged tocommunicate with a core network and/or to provide services and/orcontrol to one or more user equipments and/or to relay and/or transportcommunications and/or data between one or more user equipments and acore network and/or another base station and/or be Proximity Serviceenabled.

An eNodeB (eNB) may be envisioned as an example of a base station, e.g.according to an LTE standard. A base station may generally be proximityservice enabled and/or to provide corresponding services. It may beconsidered that a base station is configured as or connected orconnectable to an Evolved Packet Core (EPC) and/or to provide and/orconnect to corresponding functionality. The functionality and/ormultiple different functions of a base station may be distributed overone or more different devices and/or physical locations and/or nodes. Abase station may be considered to be a node of a wireless communicationnetwork. Generally, a base station may be considered to be configured tobe a coordinating node and/or to allocate resources in particular forcellular communication between two nodes or terminals of a wirelesscommunication network, in particular two user equipments.

An antenna array may comprise a plurality of antennas or antennaelements, which may be individually controllable and/or be controllablefor beamforming. An antenna array may in particular comprise 128 ormore, or 256 or more, or 512 or more antenna elements. An antenna array,and/or the network node and/or associated circuitry, may be adapted forMassive MIMO.

Resources or communication resources or radio resources may generally befrequency and/or time resources (which may be called time/frequencyresources). Allocated or scheduled resources may comprise and/or referto frequency-related information, in particular regarding one or morecarriers and/or bandwidth and/or subcarriers and/or time-relatedinformation, in particular regarding frames and/or slots and/orsubframes, and/or regarding resource blocks and/or time/frequencyhopping information. Transmitting on allocated resources and/orutilizing allocated resources may comprise transmitting data on theresources allocated, e.g. on the frequency and/or subcarrier and/orcarrier and/or timeslots or subframes indicated. It may generally beconsidered that allocated resources may be released and/or de-allocated.A network or a node of a network, e.g. an allocation or network node,may be adapted to determine and/or transmit corresponding allocationdata indicating release or de-allocation of resources to one or morewireless devices, in particular to a first wireless device. Resourcesmay be represented by resource blocks or resource elements (RE), thelatter of which may represent a smallest allocatable block oftime/frequency resource and/or a subcarrier in frequency space and asymbol time length in time, in particular for LTE.

A wireless communication network may generally be any network providingradio access for telecommunication. It may comprise a Radio AccessNetwork (RAN), e.g. according to UMTS, LTE or a related standard, a NextRadio standard or generally a 4G or 5G standard. A network node maygenerally be any radio network node, e.g. of a RAN. For example, anetwork node may be a base station, eNodeB, macro node, micro node,relay node, etc. A terminal may be any device providing a possibletermination point for telecommunication utilising the wirelesscommunication network. The terminal may be adapted for communicationwith or via the network, in particular a network node of the network. Aterminal may be implemented as a user equipment (UE), orMachine-Type-Communication (MTC) device. It may be considered that aterminal is mobile, however, stationary terminals may be envisioned. Aterminal may in particular be a smartphone, mobile phone, tablet,laptop, desktop computer, sensor arrangement or a machine adapted e.g.for MTC.

In this description, for purposes of explanation and not limitation,specific details are set forth (such as particular network functions,processes and signaling steps) in order to provide a thoroughunderstanding of the technique presented herein. It will be apparent toone skilled in the art that the present concepts and aspects may bepracticed in other embodiments and variants that depart from thesespecific details.

For example, the concepts and variants are partially described in thecontext of Long Term Evolution (LTE) or LTE-Advanced (LTE-A) or NextRadio mobile or wireless communications technologies; however, this doesnot rule out the use of the present concepts and aspects in connectionwith additional or alternative mobile communication technologies such asthe Global System for Mobile Communications (GSM). While the followingembodiments will partially be described with respect to certainTechnical Specifications (TSs) of the Third Generation PartnershipProject (3GPP), it will be appreciated that the present concepts andaspects could also be realized in connection with different PerformanceManagement (PM) specifications.

Moreover, those skilled in the art will appreciate that the services,functions and steps explained herein may be implemented using softwarefunctioning in conjunction with a programmed microprocessor, or using anApplication Specific Integrated Circuit (ASIC), a Digital SignalProcessor (DSP), a Field Programmable Gate Array (FPGA) or generalpurpose computer. It will also be appreciated that while the embodimentsdescribed herein are elucidated in the context of methods and devices,the concepts and aspects presented herein may also be embodied in aprogram product as well as in a system comprising control circuitry,e.g. a computer processor and a memory coupled to the processor, whereinthe memory is encoded with one or more programs or program products thatexecute the services, functions and steps disclosed herein.

It is believed that the advantages of the aspects and variants presentedherein will be fully understood from the foregoing description, and itwill be apparent that various changes may be made in the form,constructions and arrangement of the exemplary aspects thereof withoutdeparting from the scope of the concepts and aspects described herein orwithout sacrificing all of its advantageous effects. The aspectspresented herein can be varied in many ways.

Some useful abbreviations comprise:

Abbreviation Explanation BLER Block Error Rate CRS Cell-specific orCommon RS DCI Downlink Control Information ePDCCH enhanced PhysicalDownlink Control Channel LTE Long Term Evolution MAC Medium AccessControl MCS Modulation and Coding Scheme OFDM Orthogonal FrequencyDivision Multiple Access PDCCH Physical Downlink Control Channel PDSCHPhysical Downlink Shared Channel PRB Physical Resource Block PUSCHPhysical Uplink Shared Channel RAT Radio Access Technology RB ResourceBlock RE Resource Element RRC Radio Resource Control RS ReferenceSignal(ing) SC-FDMA Single Carrier- Frequency Division Multiple AccesssPDCCH short Physical Downlink Control Channel sPDSCH short PhysicalDownlink Shared Channel sPUSCH short Physical Uplink Shared Channel SFSubFrame sTTI short TTI (shorter than a subframe/14 symbols) SRSSounding Reference Signal(ing) TTI Transmission Time Interval PDCCHPhysical Downlink Control Channel PUSCH Physical Uplink Shared ChannelPUCCH Physical Uplink Control Channel DL Downlink; generally referringto transmission of data to a node/into a direction further away fromnetwork core (physically and/or logically); in particular from a basestation or eNodeB to a D2D enabled node or UE; often uses specifiedspectrum/bandwidth different from UL (e.g. LTE) UL Uplink; generallyreferring to transmission of data to a node/into a direction closer to anetwork core (physically and/or logically); in particular from a D2Denabled node or UE to a base station or eNodeB; in the context of D2D,it may refer to the spectrum/bandwidth utilized for transmitting in D2D,which may be the same used for UL communication to a eNB in cellularcommunication; in some D2D variants, transmission by all devicesinvolved in D2D communication may in some variants generally be in ULspectrum/bandwidth/carrier/frequency

These abbreviations may be used according to 3GPP and/or LTE practice,if applicable.

The invention claimed is:
 1. A method of operating a terminal in awireless communication network, the method comprising: receiving ortransmitting according to a transmission time interval, TTI,configuration, the TTI configuration indicating a plurality of TTIpatterns, wherein each TTI pattern includes at least one short TTIhaving between one or two and seven symbols of duration in a subframe,and wherein, within each TTI pattern, the at least one short TTI ends ata same Orthogonal Frequency Division Multiple Access, OFDM, symbol. 2.The method according to claim 1, wherein the TTI configuration isconfigured by a network node.
 3. The method according to claim 1,wherein, for each TTI pattern, the at least one short TTI is confinedwithin a slot.
 4. The method according to claim 3, wherein the slot is afirst slot in a first subframe of each TTI pattern.
 5. The methodaccording to claim 3, wherein the at least one short TTI comprises: afirst short TTI having between one or two and seven symbols of durationin a first slot of a first subframe, and a second short TTI havingbetween one or two and seven symbols of duration in another slot of thefirst subframe, wherein the second short TTI has a short TTI length thatis different from a short TTI length of the first short TTI.
 6. Themethod according to claim 1, wherein the at least one short TTIcomprises: a first short TTI having between one or two and seven symbolsof duration in a first subframe, and a second short TTI having betweenone or two and seven symbols of duration in a second subframe, whereinthe second short TTI has a short TTI length that is different from ashort TTI length of the first short TTI.
 7. A terminal for a wirelesscommunication network, the terminal comprising: processing circuitryconfigured to receive or transmit according to a transmission timeinterval, TTI, configuration, the TTI configuration indicating aplurality of TTI patterns, wherein each TTI pattern includes at leastone short TTI having between one or two and seven symbols of duration ina subframe, and wherein, within each TTI pattern, the at least one shortTTI ends at a same Orthogonal Frequency Division Multiple Access, OFDM,symbol.
 8. The terminal according to claim 7, wherein the TTIconfiguration is configured by a network node.
 9. The terminal accordingto claim 7, wherein, for each TTI pattern, the at least one short TTI isconfined within a slot.
 10. The terminal according to claim 9, whereinthe slot is a first slot in a first subframe of each TTI pattern. 11.The terminal according to claim 9, wherein the at least one short TTIcomprises: a first short TTI having between one or two and seven symbolsof duration in a first slot of a first subframe, and a second short TTIhaving between one or two and seven symbols of duration in another slotof the first subframe, wherein the second short TTI has a short TTIlength that is different from a short TTI length of the first short TTI.12. The terminal according to claim 7, wherein the at least one shortTTI comprises: a first short TTI having between one or two and sevensymbols of duration in a first subframe, and a second short TTI havingbetween one or two and seven symbols of duration in a second subframe,wherein the second short TTI has a short TTI length that is differentfrom a short TTI length of the first short TTI.
 13. A method ofoperating a network node in a wireless communication network, the methodcomprising: configuring a terminal with a transmission time interval,TTI, configuration for downlink communication and/or uplinktransmission, the TTI configuration indicating a plurality of TTIpatterns, wherein each TTI pattern includes at least one short TTIhaving between one or two and seven symbols of duration in a subframe,and wherein, within each TTI pattern, the at least one short TTI ends ata same Orthogonal Frequency Division Multiple Access, OFDM, symbol. 14.The method according to claim 13, wherein, for each TTI pattern, the atleast one short TTI is confined within a slot.
 15. The method accordingto claim 14, wherein the slot is a first slot in a first subframe ofeach TTI pattern.
 16. The method according to claim 14, wherein the atleast one short TTI comprises: a first short TTI having between one ortwo and seven symbols of duration in a first slot of a first subframe,and a second short TTI having between one or two and seven symbols ofduration in another slot of the first subframe, wherein the second shortTTI has a short TTI length that is different from a short TTI length ofthe first short TTI.
 17. The method according to claim 13, wherein theat least one short TTI comprises: a first short TTI having between oneor two and seven symbols of duration in a first subframe, and a secondshort TTI having between one or two and seven symbols of duration in asecond subframe, wherein the second short TTI has a short TTI lengththat is different from a short TTI length of the first short TTI.
 18. Anetwork node for a wireless communication network, the network nodecomprising: processing circuitry configured to configure a terminal witha transmission time interval, TTI, configuration for downlinkcommunication and/or uplink transmission, the TTI configurationindicating a plurality of TTI patterns, wherein each TTI patternincludes at least one short TTI having between one or two and sevensymbols of duration in a subframe, and wherein, within each TTI pattern,the at least one short TTI ends at a same Orthogonal Frequency DivisionMultiple Access, OFDM, symbol.
 19. A non-transitory computer readablemedium storing code executable by processing circuitry, the code causingthe processing circuitry to: receive or transmit according to atransmission time interval, TTI, configuration, the TTI configurationindicating a plurality of TTI patterns, wherein each TTI patternincludes at least one short TTI having between one or two and sevensymbols of duration in a subframe, and wherein, within each TTI pattern,the at least one short TTI ends at a same Orthogonal Frequency DivisionMultiple Access, OFDM, symbol.